Abstract
BackgroundEvidence is emerging that pain in rheumatoid arthritis (RA) exists without underlying inflammation. Our objective was to evaluate the prognostic value of pain classification at treatment initiation using the painDETECT questionnaire (PDQ). Outcomes were change in DAS28-CRP and RAMRIS synovitis score.MethodsRA patients initiating a disease-modifying anti-rheumatic drug (DMARD) or initiating/ switching a biological agent were included. Follow-up time was 4 months. Clinical examination, imaging (MRI, dynamic contrast-enhanced MRI (DCE-MRI)), and patient-reported outcomes were undertaken. The PDQ was used to differentiate pain mechanisms. Mean change (95% CI) was calculated using ANCOVA. Multivariable regression models were used to determine a prognostic value.ResultsA total of 102 patients were included; 75 were enrolled for MRI. Mean changes in baseline variables were greatest in the high PDQ classification group (> 18), while limited in the intermediate group (13–18). The 12 patients with high baseline PDQ score all changed pain classification group. No prognostic value of PDQ pain classification was found in relation to change of DAS28-CRP, RAMRIS score, or VAS pain. In the unadjusted model, RAMRIS score at baseline was associated with change in DAS28-CRP. The exploratory variables of DCE-MRI did not differ from other inflammatory variables.ConclusionsIn RA patients a high PDQ score (non-nociceptive pain) at baseline was not associated with worse outcomes, in fact these patients had numerically greater improvement in DAS28-CRP. However, pain classification by PDQ was not independently associated with change in DAS28-CRP, RAMRIS score, or VAS pain in the prognostic models.Furthermore, patients classified with a high baseline PDQ score changed pain classification group. Patients with unclear pain mechanism had reduced numerically treatment response.Trial registrationThe study was approved by the Regional Ethics Committee of the Capital of Denmark April 18 2013; identification number H-3-2013-049.
Highlights
Evidence is emerging that pain in rheumatoid arthritis (RA) exists without underlying inflammation
75 patients completed the painDETECT questionnaire (PDQ) and had an Magnetic resonance imaging (MRI) scan performed at baseline and of these, 71 patients had an MRI scan performed at follow-up
This was not confirmed in the multiple regression analysis, we found that these patients (n = 12) experienced the greatest numerical change in DAS28-C-reactive protein (CRP), self-reported disease severity measures, and objective inflammatory parameters, including MRI (Table 2)
Summary
Evidence is emerging that pain in rheumatoid arthritis (RA) exists without underlying inflammation. A substantial proportion of RA patients in stable clinical remission continue to report moderate to severe pain levels [4] and studies have indicated that RA leads to widespread pain in 10–20% of patients [5] Such observations have led to the contention that changes in the peripheral and central nervous system through processes of neural plasticity and central sensitization may play an important role [6]. A state of induced hypersensitivity of the pain system may persist in subsets of patients and lead to chronic pain states in which pain is no longer coupled to the presence of ongoing peripheral inflammation [7] In such patients, persistent pain hypersensitivity may lead to continuous high reports of tender joints and poor global health; subcomponents of the commonly used composite disease activity score of 28 joints (DAS28-CRP) and overestimation of inflammatory activity. Identification of underlying pain mechanisms has potential importance when prognosticating the effect of medical treatment on inflammation and pain
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